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JNDIAN  NOTES  E 

AND  MONOGRAPHS      5!^ 

Edited  by  F.  W.  Hodge  ,f\^?6? 

.)!     45 


A  SERIES  OF  PUBLICA- 
TIONS RELATING  TO  THE 
AMERICAN  ABORIGINES 


MORPHOLOGICAL  AND  METRL 
11  CAL  VARIATION    IN    SKULLS 

FROM   SAN   MIGUEL  ISLAND, 

CALIFORNIA 

II.    THE   FORAMEN    MAGNUM: 
SHAPE,   SIZE,   CORRELATIONS 

BY 

BRUNO  OETTEKING 


NEW  YORK 

MUSEUM   OF  "THE   AMERICAN   INDIAN 

J 
HEYE   FOUNDATION 

1928 


LANCASTER  PRESS, INC. 
LANCASTER,  PA. 


MORPHOLOGICAL  AND 

METRICAL  VARIATION 

IN  SKULLS  FROM  SAN 

MIGUEL  ISLAND, 

CALIFORNIA 


II 

THE  FORAMEN  MAGNUM: 

SHAPE,  SIZE,  COR- 

RELATIONS 


BY 

BRUNO  OETTEKING 


Digitized  by  the  Internet  Archive 

in  2011  with  funding  from 

LYRASIS  members  and  Sloan  Foundation 


http://www.archive.org/details/morphologicalmetOOoett 


CONTENTS 

1.  Introduction 7 

2.  Problem 8 

3.  Shape  of  Foramen  Magnum 9 

4.  Metrical  Definition  of  Foramen  Magnum 16 

a.  Length 16 

b.  Width. 17 

c.  Length-width  index 18 

d.  Module 20 

e.  Angular  Relation  to  Ear-eye  Plane 21 

5.  Correlations 24 

a.  Mutual  Relation  between  Absolute  Cranial 

and  Foramen  Magnum  Measure- 
ments        25 

a.  Cranial  Length  and  Foramen  Mag- 
num Length 25 

/?.  Cranial  Breadth  and  Foramen  Mag- 
num Width 29 

b.  Mutual     Relation     between     Proportional 

Evaluations 32 

a.  Cranial   Length-breadth    Index   and 

Foramen  Magnum  Index 32 

/3.  Cranial  and  Foramen  Magnum  Mod- 
ules       35 

c.  Mutual    Relation    between    the    Foramen 

Magnum  Angle  and  Absolute  and 

Proportional     Foramen      Magnum 

and  Cranial  Evaluations 37 

a.  Angle  and  Length  of  the  Foramen 

Magnum 37 

/3.  Angle    and    Index   of    the   Foramen 

Magnum 40 

y.  Foramen  Magnum  Angle  and  Cranial 

Length 42 

8.  Foramen  Magnum  Angle  and  Cranial 

Length-breadth  Index 44 

6.  Conclusion  and  Summary 47 

7.  Literature 54 


MORPHOLOGICAL  AND   METRICAL 

VARIATION   IN   SKULLS   FROM 

SAN   MIGUEL   ISLAND, 

CALIFORNIA 

II.  The  Foramen  Magnum:  Shape,  Size, 
Correlations 

By  Bruno  Oetteking 

1.     INTRODUCTION 

THE  following  study  represents  the  second  in- 
vestigation of  a  series  of  skulls  from  San 
Miguel  island,  California,  the  more  complete 
data  of  which  may  be  found  in  the  introduction  to 
the  author's  first  paper  in  this  series  on  the  Sutura 
Nasofrontalis.1  The  number  of  skulls  examined  in 
the  present  study  comprise  67  males,  16  females, 
and  4  infantiles. 

The  factors  which  govern  the  shape  and  size  of 
the  foramen  magnum,  and  its  correlative  position  in 
the  cranial  complex,  are  the  same  as  those  which 
govern  the  development  of  any  other  detail  in  the 
human  organism:  physiologic  demand  (function, 
adaptation)  and  heredity.  The  factors  of  decisive 
importance  in  our  case  are  (1)  the  marvelous  growth 
of  the  brain  in  the  course  of  mammalian  evolution, 
1  Indian  Notes  and  Monographs,  vol.  vn,  no.  2,  1920. 

7 


8  SKULLS    FROM 

and  (2)  in  connection  therewith  the  acquisition  of 
the  erect  gait.  It  was  shown  by  Bolk  (1915)  that 
the  shifting  or  migration  of  the  foramen  magnum 
from  a  postero-occipital  to  an  infero-occipital  (basi- 
lar) location  was  due  to  the  rapid  expansion  of  the 
brain,  whereas  the  modifications  of  shape  and  size 
of  the  foramen  magnum  are  influenced  by  the  erect 
gait  which  imposes  increasingly  changing  demands 
on  the  statics  and  dynamics  of  the  human  head,  as 
controlled  by  muscular  action.  Mutual  interre- 
lations prevailing  in  the  skeleton  in  general  must 
also  be  considered  in  this  connection  with  regard  to 
the  cranial  complex,  and  which  give  rise  to  corre- 
lations between  the  cranial  parts. 

So  far  as  can  be  learned,  a  systematic  investigation 
of  such  correlative  factors  does  not  appear  to  have 
been  carried  on.  Conjectures,  however,  as  to  the 
mutual  relation  between  the  size  of  the  foramen 
magnum  and  that  of  the  entire  cranium  and  stature 
are  occasionally  met  in  anthropological  literature 
(Hrdlicka,  1906,  54;  1907,  31;  1909,  195;  1916,  31- 
32;  Hooton,  1920,  98,  et  al.). 

2.     PROBLEM 

The  present  investigation  concerns  itself  with  the 
descriptive  and  metrical  interpretation  of  the 
foramen  magnum,  in  the  following  order:  (1)  shape, 
(2)  size,  (3)  angular  conditions,  and  (4)  correlative 
conditions.  These  latter  are  enhanced  by  classifi- 
catory    comparison    of    absolute    and    proportional 


SAN    MIGUEL    ISLAND  9 

measurements  of  the  foramen  magnum  with  those 
of  the  cranium  as  a  whole. 

3.     SHAPE  OF   FORAMEN   MAGNUM 

Owing  to  the  general  uncertainty  of  shape  of  the 
foramen  magnum,  it  is  rather  difficult  from  the 
cranioscopic  angle  to  describe  or  point  out  definite 
and  unmistakable  types  in  a  given  series.  Its 
variableness  may  well  be  likened  to  that  of  the 
cranial  form  itself.  While  in  this  latter  respect  a 
number  of  individuals  may  be  grouped  around  more 
primary  or  conservative  types,  a  certain  prevalence 
of  shape  may  obtain  also  with  regard  to  the  foramen 
magnum.  Such  primary  forms  may  be  the  elliptic 
and  circular  ones  which,  however,  even  if  true  to 
type,  only  rarely  represent  racial  characters  of  diag- 
nostic value.  In  this  respect  the  modifications  of 
the  primary  shapes  are  of  far  greater  occurrence. 
Hooton  (1920,  112)  thus  distinguishes  in  the  Madi- 
sonville  crania  between  irregular,  half-diamond, 
round,  diamond,  and  hexagonal,  while  the  present 
author  in  the  Jesup  Report  (1929)  recognizes  round 
and  elliptic  as  fundamental  shapes  with  modifica- 
tions in  the  rhomboid,  and  in  the  oval  with  anteriorly 
or  posteriorly  situated  bases.  A  racial  prevalence 
may  at  times  be  encountered,  as  Haberer  (1902,  87), 
for  instance,  claims  of  the  Chinese  when  he  says, 
"  Das  Foramen  magnum  ist  gewohnlich  gross,  rhom- 
bisch  und  hat  rauhe  dicke  Rander,"  or  Klaatsch 
(1908,    127),  of  the  Australians,  stating  that  "the 


to  u 


i^b 


5.2 


^        -  o 


X   Si 

s  > 

s  o 


Coo 
— r-^ 


=3^?. 


J3 


SAN    MIGUEL    ISLAND        11 

diameter  of  the  foramen  shows  much  variation,  an 
oval  shape  being  the  prevailing  rule,"  but  men- 
tioning also  circular  forms. 

In  the  series  under  discussion  the  author  has 
applied  the  distinction  of  shapes  as  described  in  the 
preceding  paragraph  without,  however,  accounting 
for  the  anteriorly  pointed  oval  and  the  rhomboid, 
true  instances  of  which  were  not  available.  Regard- 
ing the  latter  it  should  be  mentioned  that  the 
projection  of  the  occipital  condyles  into  the  lumen 
of  the  foramen  magnum  frequently  causes  the 
erroneous  impression  of  a  rhomboid  foramen 
magnum  which  in  fact  it  is  not.  It  must  further- 
more be  remembered  that  since  true  types  are  rather 
rare,  their  modifications  are  somewhat  difficult  to 
recognize,  and  their  classification,  therefore,  is  some- 
what arbitrary.  Thus,  elliptic  and  oval  shapes 
may  be  very  similar,  while  both  may  be  quite  wide 
and  show  affinity  to  the  circular  shape. 

Taking  all  these  fallacies  into  consideration  the 
following  distinction  was  finally  decided  on:  (1)  ellip- 
tic, (2)  circular,  and  (3)  anteriorly  pointed  oval, 
which  may  be  seen  illustrated  in  fig.  1,  a-c,  after 
specimens  in  the  series  under  discussion.  Their 
distribution  among  our  series  is  shown  in  Table  I, 
where  the  percental  participation  of  the  different 
shapes  is  highest  in  the  circular,  slightly  less  in  the 
elliptic,  and  still  less,  although  at  an  appreciable 
figure  of  21.7%,  in  the  oval.  The  distribution 
among  the  sexes  is   quite  interesting.     Equal   fre- 


12 


SKULLS    FROM 


Table  I.     Actual  and  Percental  Frequency  of  Foramen 
Magnum  Shapes 


Classes 

Elliptic 

Circular 

Oval 

anteriorly 
pointed 

Total 

31 

37.3% 

34 

41.0% 

18 

21.7% 

c? 

9 

Inf 

26 

5 

83.9% 
16.1% 

25 

7 
2 

73.5% 

20.6% 

5-9% 

15 
3 

83.3% 
16.7% 

quencies  of  the  elliptic  and  oval  shapes  occur  in  the 
males  at  83%  and  in  the  females  at  16%,  while  in 
the  circular  there  is  a  relatively  lesser  frequency  in 
the  males  and  a  higher  one  in  the  females.  The  two 
infantiles  are  also  listed  in  the  column  headed 
circular. 

Irregularities  around  the  foramen  magnum,  such 
as  the  various  "manifestations  of  the  occipital 
vertebra"  (Kollmann,  Bolk),2  or  others  resulting 
from  pathological  or  mechanical  causes,  do  not 
obtain  in  our  series.  There  is,  however,  a  vari- 
ation in  the  posterior  border  of  the  foramen  which 
deserves  mention.  In  ontogenetic  stages  an  inde- 
pendent bone,  medially  situated,  is  derived  from  a 
special  ossification  center  in  the  cartilaginous 
matrix,  Hannover1  s  (1881)  membrana  spinoso-occipi- 
talis.  Normally  this  small  bone  in  proper  time, 
i.e.  several  years  after  birth,  according  to  Gegenbaur 

2  See  Oetteking,  Bruno,  1923. 


SAN    MIGUEL    ISLAND        13 


Fig.  2. — Anlage  of  an  ossiculum  Kerckringii  (Topinard),  x,  in  a 
fetal  human  os  occipitale.  (After  Cunningham,  D.  J.,  Textbook  of 
Anatomy,  1923,  p.  196.) 


14  SKULLS    FROM 

in  the  sixth  to  seventh  year,  merges  with  the  sur- 
rounding occipital  parts.  This  osseous  element  is 
the  ossiculum  Kerckringii  (Topi?iard),  or  manubrium 
squamae  occipitalis  (R.  Virchow),  the  anlage  of  which 
is  shown  in  the  fetal  bone  of  fig.  2.  In  rare  cases 
it  does  not  merge,  and  this  produces  an  emargin- 
ation  with  more  or  less  sharp  edges  which  then 
causes  an  elongation  of  the  foramen.  Our  series 
does  not  contain  such  cases;  a  number  of  them 
instead,  however,  show  peculiar  shapings  of  the 
opisthion  region  which  bear  evidence  of  individu- 
ally variable  ossification.  They  are  easily  definable 
as  straight  and  more  or  less  angularly  set  off  against 
the  lateral  margins  of  the  foramen  magnum,  or  as 
concave  or  convex.  In  fig.  3,  a-e,  these  variations 
are  illustrated,  a  representing  the  normal  condition 
of  an  even  rounding,  as  in  no.  314  9  of  our  series. 
A  straight  line,  10  mm.  in  length,  forming  mildly 
obtuse  angles  at  both  ends,  ma}^  be  noticed  in  b. 
It  is  an  immature  skull  of  the  infant  I  stage,  no.  267, 
the  permanent  molars  not  having  erupted  as  yet. 
This  is  a  particularly  interesting  case  because  of  the 
fact  that  the  two  lateral  sutures  (fissures?)  at  each 
end  of  the  straight  line  had  not  become  obliterated, 
which  corroborates  Gegenbaur's  statement,  referred 
to  above,  of  mergence  of  the  ossiculum  Kerckringii 
during  childhood.  A  modification  of  fig.  3,  b,  is 
pictured  in  c,  corresponding  to  no.  337  d71  of  our 
series,  where  the  straight  line  that  marks  the  medial 
posterior  edge  of  the  foramen  magnum  turns  sharply 


flit-      ®Wif        l^''^»ii'-A,«\v!is        t^t>T^a,K\  jmt-v- ■*"-..?■»*        i?" 


Fig.  3. — Variation  in  the  anomalous  emargination  of  the  posterior  border  of  the  foramen  magnum.     See  text.     Slightly  reduced. 


SAN    MIGUEL    ISLAND        15 

forward  at  right  angles.  These  side  lines  again  form 
more  or  less  pronounced  angles  with  the  lateral 
margins  of  the  foramen  magnum.  If  the  latter 
were  connected  with  one  another  from  side  to  side, 
a  rectangle  of  only  3  mm.  in  depth  and  10  mm.  in 
width  would  result.  The  concave  shape,  as  given 
in  d  of  our  figure,  is  that  of  no.  272  cf ;  it  represents 
a  neatly  shaped  notch,  while  in  e,  no.  301,  inf.  II, 
where  the  medial  portion  bulges  out  and  produces 
a  convexity  forward,  this  seems  to  be  partly  filled 
in  again.  Most  of  these  shapes  represent  single 
occurrences  in  our  series,  and  might  be  attributed 
directly  to  irregular  ossification.  A  deficiency  there 
of  the  independent  osseous  element  hardly  comes 
under  consideration,  since  the  notches  are  not  deep 
enough  to  justify  such  an  assumption.  Nor  on 
account  of  their  scarcity  can  they  be  regarded  as  a 
racial  trait,  although  Klaatsch  (1908,  127  and  plates) 
has  repeatedly  observed  them  in  his  Australian 
skulls,  and  Cameron  (1923,  41c)  in  the  Eskimo.  But 
even  in  pronounced  cases  of  absence  of  the  ossiculum 
Kerckringii,  such  a  condition  must  not  be  mistaken 
for  knife-marks  caused  in  maceration  which  at  times 
occur  somewhat  regularly  and  which  Hrdlicka  (1907, 
91)  mentions  in  discussing  the  Gilder  Mound  crania 
of  Nebraska. 


16  SKULLS    FROM 

4.     METRICAL   DEFINITION   OF 
FORAMEN    MAGNUM 

a.   Length 

The  physiological  range  of  the  length  of  the 
foramen  magnum  in  our  series  is  almost  identical  in 
the  sexes,  extending  from  29-38  mm.  in  the  males 
and  from  29-37  mm.  in  the  females,  while  the  two 
immatures  measure  31  mm.  and  33  mm.  This  is 
fairly  in  accord  with  Martin's  (1928,  851)  statement 
of  a  total  physiological  range  of  (25  mm.)  30  mm.  to 
40  mm.  (43  mm.)  where  the  parenthesized  figures 
represent  the  extreme  values  of  a  Bashkir  and  a 
Tyrolese  in  the  order  of  the  citation.  The  averages 
amounting  to  33.6  mm.  in  the  males,  32.8  mm.  in 
the  females,  and  32.0  mm.  in  the  immatures, 
although  quite  similar,  exhibit  nevertheless  such 
differences  as  are  generally  met  between  the  sexes, 
as  well  as  between  the  mature  and  immature  ages, 
i.e.  the  male  values  exceeding  the  female,  and  the 
latter  the  immatures.  If  compared  with  other 
human  groups,  the  foramen  magnum  length  in  our 
series  is  rather  small,  as  may  be  seen  in  Table  II.3 
The  Japanese  as  well  as  the  Australian  averages 
exceed  those  of  our  series,  and  the  La  Chapelle-aux- 
Saints  value  of  46  mm.  appears  to  be  the  highest 
on  record. 

3  Comparative  data  here  as  elsewhere  are  in  most  cases 
quoted  from  Rud.  Martin,  Lehrbuch  der  Anthropologic 
(1928). 


SAN    MIGUEL    ISLAND 


17 


Table  II.     Comparative  Averages  of  the  Foramen 
Magnum  Length 


Classes 

Length  of  foramen  magnum  (averages) 

San  Miguel 
Island 

Japanese 

Australians 

La  Chapelle- 
aux-Saints 

c7" .-.'.. 

9  .... 
Inf.... 
Range. 

33.6  mm.  (67) 

32.8  mm.  (16) 

32.0  mm.  (  2) 

29-38  mm.  (85) 

36.5  mm. 
36.5  mm. 

35.5  mm. 
34.0  mm. 

46  mm. 

b.   Width 

The  range  of  the  foramen  magnum  width,  like 
the  length,  comprises  10  units,  extending  from  24-33 
mm.,  which  at  the  same  time  represents  our  male 
range,  the  female  extending  from  24-31  mm.,  and 
that  of  the  four  infantiles  from  26-28  mm.  Martin's 
(1928,  851)  general  range  comprises  individual  width 
values  from  (20  mm.)  23  mm.  to  38  mm.  where  the 
parenthesized  low  extreme  is  that  of  a  Roumanian. 
Our  highest  value  of  33  mm.  is  thus  seen  to  fall 
noticeably  short  of  Martin's  highest  one.  Our 
averages  of  28.6  mm.,  27.3  mm.,  and  27.0  mm.  in 
the  sexes  and  immatures,  as  listed  in  Table  III, 
show  a  tendency  toward  smallness.  The  width 
averages  manifest  similar  diversities  to  those  found 
in  the  length  averages.  Comparison  of  these 
figures  and  those  of  the  other  human  varieties  quoted 
in  Table  II  reveals  similar  proportions  within  each 
set  of  averages.      It  must  be  noted,  however,  that 


18 


SKULLS    FROM 


the  average  of  the  foramen  magnum  width  in  the 
Japanese  females  at  26.5  mm.,  considering  the 
smallness  of  the  measurement,  is  markedly  less 
than  that  of  the  Japanese  males,  as  against  the 
equality  of  their  foramen  magnum  length  measure- 
ments at  36.5  mm.  The  foramen  magnum  width 
of  the  La  Chapelle-aux-Saints  skull  falls  likewise 
considerably  short  of  its  excessive  length,  being 
thus  rather  comparable  with  the  male  width  average 
of  the  Japanese,  which  in  turn  is  slightly  in  excess 
of  the  width  average  of  our  own  series. 


Table  III.     Comparative  Averages  of  the  Foramen 
Magnum  Width 


Classes 

Width  of  foramen  magnum  (averages) 

San  Miguel 
Island 

Japanese 

Australians 

La  Chapelle- 
aux-Saints 

9  .... 
Inf.... 
Range. 

28.6  mm.  (67) 

27.3  mm.  (16) 

27.0  mm.  (14) 

24-33  mm.  (87) 

30.3  mm. 
26.5  mm. 

29.9  mm. 
29.3  mm. 

30  mm. 

c.   Length- width  Index 

The  total  range  of  the  foramen  magnum  index  is 
very  extensive  between  the  extreme  values  of  71.4 
and  103.5,  both  being  males.  The  female  range 
between  72.7  and  93.1  is  less  extended,  while  the 
two  infan tiles  have  indices  of  81.8  and  83.9.  In 
correspondence    with    the    length-width    differences 


SAN    MIGUEL    ISLAND 


19 


within  and  between  the  sexes,  the  male  average  of 
84.8  slightly  exceeds  the  female  of  83.2.  This 
condition  is  much  more  marked  in  the  Japanese  of 
Table  IV,  whose  considerably  smaller  female  average 


Table  IV.     Comparative  Averages  of  the  Foramen 
Magnum  Index 


Classes 

Foramen  magnum  index 

San  Miguel 
Island 

Japanese 

Australians 

La  Chapelle- 
aux-Saints 

9  .... 
Inf.... 
Range. 

84.8  mm.  (67) 

83.2  mm.  (16) 

82.0  mm.  (2) 

71.4- 

103.5  mm.  (85) 

83.4  mm. 
72.6  mm. 

84.9  mm. 
86.1  mm. 

65.2  mm. 

— 

is  the  result  of  the  noticeably  lesser  female  foramen 
magnum  width  as  against  the  higher  male  width  and 
the  equality  of  the  foramen  magnum  length  in  the 
Japanese  sexes  of  Table  II.  The  La  Chapelle-aux- 
Saints  index  of  65.2  appears  to  be  the  smallest  on 
record,  owing  to  the  excessive  length  and  the 
relatively  small  width  of  this  fossil's  foramen 
magnum.4  From  Martin's  (1928,  851-852)  figures 
it  may  be  gathered  that  the  physiologic  range  of  the 
foramen  magnum  index,  71-111,  is  very  extensive 
and  comparable  somewhat  to  the  range  of  the  series 

4  See,  however,  Table  XI  (Eskimo)  and  accompanying 
text  on  page  34. 


20  SKULLS    FROM 

under  discussion.  The  average  of  the  latter  when 
judged  by  Martin's  list  of  racial  averages  occupies  a 
submedium  position,  thus  indicating  a  slight  ten- 
dency toward  a  bilaterally  narrowing  circular  form. 
They  are  exceeded  toward  the  other  extreme  by  a 
number  of  varieties  like  the  Bavarians,  Malays, 
Paltacalo  Indians,  and  others.  In  the  majority 
of  cases  the  female  average  falls  short  of  the  male, 
which  speaks  for  a  rounder  foramen  magnum  in 
the  latter.  The  reverse  is  shown  in  the  Australians 
of  Table  IV. 

d.   Module 

Inasmuch  as  there  is  considerable  irregularity 
and  little  special  significance  in  the  ratio  between 
the  two  main  diameters  of  the  foramen  magnum, 
Hrdlicka  (1916,  31-32),  for  comparative  purposes, 
prefers  the  foramen  magnum  module  according  to 

the    formula « •     The    sex    differences 

here,  of  course,  correspond  to  those  of  the  index, 
i.e.  there  is  a  slight  diminution  in  the  female  average. 
Thus,  while  the  male  average  of  the  module  amounts 
to  30.9,  at  a  range  from  27.0-35.0,  the  female  average 
yields  29.7  at  a  slightly  smaller  range  from  27.5- 
33.5.  The  two  infants  fall  within  the  general  range 
of  variation  with  values  of  28.5  and  30.0.  The  fol- 
lowing table  lists  a  few  comparative  data,  where 
those  of  the  other  Indians  are  quoted  from  Hrdlicka 
(1916,  32). 

It  will   be  noticed   that  the  San   Miguel   Island 


SAN    MIGUEL    ISLAND 


21 


Table  V.      Comparative  Averages  of  the  Foramen 
Magnum  Module 


Classes 

Foramen  magnum  module 

San  Miguel 
Island 

Arkansas 

Munsee 

La  Chapelle- 
aux-Saints 

&..  .. 

9  .... 

Inf.... 
Range. 

30.9  mm.  (67) 

29.7  mm.  (16) 

29.3  mm.  (2) 
27.0-35.0  mm. 

33.0  mm. 

(22) 
31.0  mm. 

(16) 

35.0  mm. 

(7) 
32.0  mm. 

(8) 

31.0- 
38.0  mm. 
(15) 

38.0  mm. 

averages  are  exceeded  by  the  Arkansas  and  Munsee, 
and  these  again  by  the  Chapelle-aux-Saints  module 
of  38.0  mm.  A  module  of  the  same  height  occurs 
in  the  Munsee  range  as  listed  in  Table  V. 


e.  Angular  Relation  to  Ear-eye  Plane 

The  angle  is  formed  by  the  basion-opisthion  line 
representing  the  foramen  magnum  plane,  and  the 
ear-eye  plane,  or  better,  its  parallel  through  the 
basion.  Using  Broca's  terminology,  the  angle  is 
positive  (  +  ),  if  situated  above  that  parallel,  and 
negative  (  — ),  if  situated  below  it.  Both  angles 
open  posteriorly.  In  fig.  4  these  conditions  are 
schematically  illustrated.  The  positive  angle,  con- 
sidered from  a  morphologic  viewpoint,  is  a  primitive 
condition  found   in  Simiidae  where  it   ranges    from 


22  SKULLS    FROM 

+  55°  (Cebus)  to  +  19°  (Gorilla).  More  advanced 
conditions  obtain  in  the  extinct  and  recent  varieties 
of  Homo,  while  in  the  Hominidse  as  shown  in  the 
La  Chapelle-aux-Saints  skull,  the  more  primitive 
angle  of  +  7°  occurs.  However,  instances  of 
positive    angles   occur   also   in    almost   any   human 


Fig.  4. — -Schematic  representation  of  the  deviations  of  the  foramen 
magnum  plane  from  a  parallel  of  the  ear-eye  plane  (e-e')  passing 
through  the  basion.  +  angle  above,  —  angle  below,  the  parallel; 
ba,  basion;   o,  opisthion. 


variety,  while  the  general  behavior  here  is  that  of  an 
advanced  morphologic  state  as  signified  by  the 
preponderance  of  the  negative  angle.  In  Europeans 
Fr.  Sarasin  (1916-1922,  195)  states  an  average  of 
—  12°,  while  in  New  Caledonians  the  males  yielded 
an  average  of  —  3°,  the  females  of  —  6.7°.  Com- 
pared with  these  findings  the  San  Miguel  Island 
averages  and  those  of  the  western  Eskimo  of  Table 
VI  range  somewhat  higher,  falling  in  fact  between 
the  more  primitive  New  Caledonians  and  the  more 
advanced  Europeans.  One  feature,  however,  is 
common,  or  at  least  preponderant,  in  all  the  vari- 
eties,   i.e.    the   greater   minus   angle   in    the   female 


SAN    MIGUEL    ISLAND 


23 


skulls  which  probably  is  due  to  the  sex  differences 
in  general  cranial  structure. 

In  the  present  series  only  one  instance  of  a 
positive  angle  has  been  met,  the  general  range 
beginning  at  +  3°  and  extending  to  —  22°.  The 
averages  yield  angles  of   —  9.4°  for  the  males  and 

—  13.2°  for  the  females,  and  from  whose  range  of 

—  5°  to    —  22°  a  higher  average  might  have  been 
anticipated.     The   two   immatures    have    angles   of 

—  7°  and   -  11°. 


Table  VI.     Comparative  Averages  of  the  Foramen 
Magnum  Angle 


Classes 

Foramen  magnum  angle 

San  Miguel 
Island 

Eskimo5 

Alaska  and 

Siberia 

Chinook 
(deformed) 

cf  .... 
9  .... 
Inf.... 
Range. 

-  9.4°  (67) 
-  13.2°  (14) 

-  9.0°  (2) 
+  3°  to  -  22° 

(83) 

-  7.1°  (32) 

-  9.8°  (12) 

+  2°  to  -  19° 
(44) 

+  0.6°  (56) 
-  0.5°  (24) 

+  14°  to  -  15° 
(80) 

It  is  of  interest  in  this  connection  to  compare  the 
status  of  the  foramen  magnum  angle  in  a  deformed 

5  The  data  of  the  last  two  columns  of  Table  VI  are  from 
the  present  author's  report,  now  in  print,  on  the  North 
Pacific  crania  of  the  Jesup  Expedition.  Regarding  the 
Chinook  findings,  see  also  Oetteking,  Bruno  (1924),  Dec- 
lination of  the  Pars  Basilaris  in  Normal  and  Artificially 
Deformed  Skulls,  Ind.  Notes  Monogr.,  misc.  27. 


24  SKULLS    FROM 

group.  Among  the  skulls  mentioned  in  footnote  5, 
there  is  a  series  of  56  male,  24  female,  5  infantile, 
and  4  juvenile  Chinook  skulls.  This  tribe,  as  is 
known,  practised  excessive  anteroposterior  skull 
deformation  which,  besides  causing  considerable 
distortion  in  the  configuration  of  the  skull  parts, 
brought  about  changes  at  the  base  of  the  skull.  The 
total  range  of  variation  comprises  angles  from 
+  14°  to  —  15°,  and  it  is  quite  significant  that  the 
infantile  and  juvenile  ranges  contain  only  plus  values 
+  7°  to  +  4°  in  the  former,  and  +  8°  to  0°  in  the 
latter,  while  the  male  and  female  ranges  extending 
into  the  minus  region  amount  to  +  14°  to  —  15° 
in  the  former,  and  +  7°  to  —  10°  in  the  latter. 
The  averages  accordingly  aggregate  +  0.6°  in  the 
males,  —  0.5°  in  the  females,  +  5.2°  in  the  in- 
fancies, and  +  3.0°  in  the  juveniles. 

5.     CORRELATIONS 

The  morphological  interpretation  of  so  complex  a 
unit  as  the  human  skull  must  needs  rely,  to  its 
greater  extent,  on  quantitative  determinations. 
Diameters  and  their  proportional  relations  expressed 
in  percental  indices,  however,  do  not  fully  solve  the 
problem:  they  disclose  only  insufficiently  the  inter- 
dependence of  parts  in  the  configurative  sense. 
Thus,  while  quantitative  determination  must  be 
the  basis  of  all  differential  treatment,  the  inter- 
pretation of  form  may  be  greatly  aided  through  the 


SAN    MIGUEL    ISLAND        25 

examination  of  the  correlations  of  parts  that  form 
the  complex.  Although  different  methods  were 
applicable  and  suitable  to  our  specific  use,  the 
counterposition  of  metrical  findings  was  preferred, 
the  problem  thus  treating  of  the  correlation  between 
the  dimensions,  shape,  angular  position  of  the 
foramen  magnum,  and  certain  cranial  dimensions 
and  proportions. 

In  the  order  of  their  importance  the  investigation 
of  mutual  relation  was  carried  on,  first,  between 
absolute  measurements  of  the  foramen  magnum  and 
the  cranium;  secondly,  between  their  proportional 
evaluations;  thirdly,  between  the  foramen  magnum 
angle,  and  absolute  foramen  magnum  and  cranial 
measurements,  and  the  proportional  evaluations  of 
the  latter. 

a.   Mutual  Relation  between  Absolute 

Cranial  and  Foramen  Magnum 

Measurements 

a.   cranial  length  and  foramen  magnum 

LENGTH 

The  averages  of  cranial  length  in  the  present  series 
amount  to  177.0  mm.  and  170.1  mm.  in  the  sexes, 
and  160.7  mm.  in  the  infantiles.  They  show  the 
usual  sex  difference,  ranging  rather  low  when  com- 
pared to  other  racial  averages  given  by  Martin 
(1928,  765)  with  male  and  female  ranges  of  174  mm. 
(Bashkirs)    to    187    mm.    (Scotch),    and    165    mm. 


26 


SKULLS    FROM 


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SAN    MIGUEL    ISLAND        27 

(Telengets)  to  179  mm.  (Scotch)  respectively.  In 
Table  VII  the  length  averages  of  the  cranium  and 
the  foramen  magnum  of  our  own  series  are  con- 
trasted with  those  of  another  group  and  a  neander- 
taloid  specimen. 

From  this  tabulation  it  appears  that  an  increasing 
cranial  length  as  represented  by  the  sex  averages  is 
associated  with  an  increasing  foramen  magnum 
length,  a  fact  which  is  evident  in  our  own  series  as 
well  as  in  the  Eskimo  and  the  human  fossil  listed 
there.  As  to  the  differential  correlation  between  the 
two  diameters  under  investigation  within  our  series, 
the  cranial  length  as  shown  in  Table  VIII  was  divided 
into  three  classes,  containing  the  individual  values 
from  164-169  mm.,  170-179  mm.,  and  180-189  mm., 
and  the  foramen  magnum  length  computed  for  each 
of  these  classes.  The  infantiles,  on  account  of 
their  small  number,  have  not  been  listed  in  the 
tables,  but  are  mentioned  in  each  case  in  the 
discussion. 

In  the  males,  the  foramen  magnum  length  for  the 
division  of  smallest  cranial  length  with  34.8  mm. 
slightly  exceeds  that  for  the  medium  class  with  an 
average  of  33.0  mm.,  only  to  increase  again  to  34.7 
mm.  with  the  class  of  greatest  cranial  length.  It  is 
quite  possible  that  the  disparity  of  successive  in- 
crease in  the  male  averages  is  due  to  the  small 
number  of  cases  in  the  class  of  lowest  cranial  length. 
The  fact,  however,  that  high  individual  values  occur 
there   cannot   be   disputed.     In   the  females   whose 


28 


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the  first  two  classes, 
the  smaller  cranial 
length  combines  itself 
with  the  lower  average 
of  the  foramen  magnum 
length,  while  the  me- 
dium class  shows  an 
increase  over  the  two. 
Two  infantile  skulls 
with  foramen  magnum 
lengths  of  31  mm.  and 
33  mm.,  as  specified  in 
Table  VII,  have  smaller 
cranial  lengths  of  161 
mm.  and  166  mm., 
which  establishes  the 
expected  correlation  be- 
tween the  two  mea- 
surements. Some  sig- 
nificance, however, 
seems  to  attach  to  the 
ranges  of  the  foramen 
magnum  length  classes 
as  correlated  with 
those  of  the  cranial 
length.  Thus,  while 
the  female  ranges  show 
an  even  increase,  the 
male    ranges    are    per- 


SAN    MIGUEL    ISLAND       29 

fectly  irregular,  which  may  be  due  in  part  to  the 
small  number  of  cases  in  the  class  of  shortest 
cranial  lengths,  as  pointed  out  above. 

|8.     CRANIAL   BREADTH   AND   FORAMEN   MAGNUM 

WIDTH 

The  two  breadth  measurements,  the  cranial  and 
that  of  the  foramen  magnum,  have  been  treated  in 
the  same  way  as  the  respective  lengths  in  the  pre- 
ceding section.  In  Table  IX  both  measurements 
are  contrasted. 

On  the  basis  of  Martin's  (1928,  766)  list  where  the 
male  averages  for  the  cranial  breadth  range  from 
128  mm.  (Vedda)  to  153  mm.  (Buriats),  and  the 
female  from  124  mm.  (Vedda,  Paltacalo  Indians) 
to  145  mm.  (Swiss  [Wallis],  Telengets),  showing  the 
usual  sex  differences,  the  San  Miguel  averages  as 
recorded  in  Table  IX  must  be  characterized  as  rather 
submediun.  There  are  also  among  the  individual 
values,  if  compared  with  Martin's  physical  range  of 
from  101-173  mm.,  only  few  above  medium  condi- 
tions. The  La  Chapelle-aux-Saints  skull,  quite  in 
proportion  with  its  inordinate  length,  is  seen  to 
exceed  in  cranial  breadth  any  of  the  San  Miguel  and 
Eskimo  specimens,  while  the  latter  exceed  the  San 
Miguel  skulls  by  only  a  trifle.  As  regards  the 
foramen  magnum  width  of  the  La  Chapelle-aux- 
Saints  skull,  this  falls,  with  30  mm.,  about  half-way 
between  the  extreme  values  of  the  Eskimo  male 
range,  a  relation  which  will  be  of  significance  in  the 


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and  length-width 
indices  treated  in 
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tion. 

Comparable  to 
the  length  mea- 
surements of  the 
San  Miguel  Island 
skulls,  those  of 
the  cranial 
breadth  and  the 
foramen  magnum 
width  show  sim- 
ilar correlations. 
There  is  in  the 
two  groups  of 
Table  IX  an  in- 
crease of  the  for- 
amen magnum 
width  observable 
along  with  the  in- 
crease of  the  cran- 
ial breadth.  If, 
however,  the 
cranial  breadth  is 
divided  into  suc- 
cessive small 
groups,  to  which 
the  foramen  mag- 


SAN    MIGUEL    ISLAND 


31 


num  width  is 
brought  in  propor- 
tion, such  a  corre- 
lation becomes  less 
evident,  as  is  shown 
in  Table  X.  Here 
the  range  of  the 
cranial  breadth  is 
divided  into  four 
classes  and  the  for- 
amen magnum 
widths  correlated 
with  each  of  them. 

As  is  the  case  in 
the  length  measure- 
ments, in  the  females 
there  is  to  be  noticed 
an  increase  in  the 
two  successive 
classes  with  averages 
of  26.8  mm.  and  27.9 
mm.,  which  is  like- 
wise obvious  in  the 
two  ranges,  24-28 
mm.  against  26-30 
mm.  Such  an  in- 
crease is  less  clear  in 
the  males,  each  of 
whose  four  class 
averages  amounts  to 


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32  SKULLS    FROM 

28  mm.  and  fractions,  and  it  is  only  by  the  latter 
and  by  the  ranges  of  the  four  classes  that  an  in- 
crease, however  slight,  may  be  realized.  Four  infan- 
cies with  cranial  breadths  between  129-138  mm. 
have  also  small  foramen  magnum  widths  of  an 
increasing  order  from  26-28  mm. 

b.   Mutual  Relation  between  Propor- 
tional Evaluations 

a.  cranial  length-breadth  index  and 
foramen  magnum  index 

The  averages  of  the  cranial  length-breadth  index 
show  the  typical  increase  in  the  order  males,  females 
and  infantiles,  and,  with  the  exception  of  the  latter 
who  are  brachycranial,  fall  into  the  mesocranial 
class.  This  is  also  true  of  the  Eskimo  included  in 
Table  XL  In  the  San  Miguel  skulls  the  averages  of 
the  foramen  magnum  index  when  compared  with 
those  of  the  cranium  show  a  gradual  decrease  as 
against  the  increasing  cranial  averages.  These 
conditions,  however,  are  reversed  in  the  Eskimo  in 
such  a  way  that  with  the  increase  of  sex  averages  the 
foramen  magnum  index  likewise  increases.  This 
being  also  the  case  with  the  Australians  of  Table  IV, 
it  may  be  assumed  that  the  proportions  between  the 
averages  of  the  foramen  magnum  index  in  the 
various   groups   of   mankind   vary   as   to   sex.     The 


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lowest  foramen  mag- 
num index  of  65.2  of 
Table  XI  (La  Chapelle- 
aux-Saints),  to  which 
reference  was  made  on 
page  19,  is  exceeded 
by  the  still  lower  male 
value  of  62.8  in  our 
Eskimo  group  and 
which  is  naturally  an 
extraneous  case,  the 
next  higher  being  73.0 
in  the  same  range. 

The  comparison  of 
the  foramen  magnum 
and  cranial  length- 
breadth  indices  in  our 
series  within  definite 
subdivisions  of  the 
latter,  as  shown  in 
Table  XII,  reveals  the 
fact  of  a  gradual  in- 
crease in  the  averages 
of  those  subdivisions 
in  the  sexes.  This  is 
in  contrast  to  the  gen- 
eral behavior  of  the  sex 
averages  as  pointed  out 
in  the  preceding  para- 
graph. 


SAN    MIGUEL    ISLAND 


35 


j8.      CRANIAL 
AND      FORAMEN 
MAGNUM      MOD- 
ULES 

Both  modules 
depend  entirely 
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dimensions  i  n 
general  and  rep- 
resent as  such 
synthetic  size 
expressions, 
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rally in  the  sexes 
in  such  a  way 
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averages  exceed 
the  female,  and 
these  in  turn 
the  infantile. 
This  is  likewise 
the  case  with 
the  foramen 
magnum  modu- 
les as  shown  in 
Table  XIII.  On 
account  of  their 
greater  cranial 
dimensions,    the 


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Eskimo  of  the  same 
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ial modules  to  which 
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modules  are  in  propor- 
tion. The  highest 
values  of  our  table, 
of  which  only  the  for- 
amen magnum  module 
of  38.0  is  doubled  in 
the  Eskimo  female 
range,  are  those  of  the 
La  Chapelle-aux-Saints 
fossil  whose  cranial 
measurements,  at  least 
the  length  and  breadth, 
were  found  to  exceed 
by  far  the  averages  and 
ranges  of  the  other 
groups  of  our  tables,8 
this  holding  true  also 
of  the  foramen  mag- 
num length.  The  high 
foramen  magnum  mod- 
ule of  the  La  Chapelle- 
aux-Saints   skull   is    ac- 

8  For  the  cranial  height 
Boule  gives  131  mm.,  a 
value  falling  well  within 
the  San  Miguel  and  Es- 
kimo series. 


SAN    MIGUEL    ISLAND        37 

counted  for  by  the  length  rather  than  by  the  for- 
amen magnum  width. 

In  the  correlation  scheme  of  Table  XIV  it  is  made 
manifest  that  in  the  males  as  well  as  in  the  females 
of  the  San  Miguel  Island  series  the  averages  of  the 
foramen  magnum  modules  increase  proportionately 
in  the  successive  classes  of  the  cranial  module. 

c.  Mutual  Relation  between  the  Foramen 
Magnum  Angle  and  Absolute  and  Pro- 
portional Foramen  Magnum  and  Cranial 
Evaluations 

a.  angle  and  length  of  the  foramen 

MAGNUM 

From  Table  VI  it  was  gathered  that  the  sex  aver- 
ages for  the  foramen  magnum  angle  differed  in  such 
a  way  that  the  female  average  yielded  the  higher 
figure,  i.e.  higher  minus  value,  thus  representing  a 
more  advanced  morphologic  condition.  This  held 
true  not  only  for  the  San  Miguel  Island  series,  but 
also  for  the  Eskimo  of  the  same  table,  and  it  may  be 
inferred  that  this  is  quite  probably  the  general 
behavior  in  the  human  groups.9 

9  From  the  physeotypical  viewpoint  one  may  be  led  to 
assume  that  the  tendency  toward  greater  female  short  - 
headedness  in  the  comparative  sense  as  a  response  probably 
to  the  less  extensive  backward  and  the  more  intensive 
lateral  and  downward  expansion  of  the  brain  (Bolk,  1915), 
influences  the  orientation  of  the  foramen  magnum  plane 
in  such  a  way  as  to  force  the  opisthion  region  downward, 
as  against  the  more  conservative  basion  region,  which  then 
would  account  for  the  greater  minus  angle  of  the  foramen 
magnum  plane. 


38 


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SAN    MIGUEL    ISLAND 


39 


The  combination  in 
Table  XV  of  the  sex 
averages  of  the  foramen 
magnum  length  and 
angle  demonstrates, 
from  the  purely  met- 
rical viewpoint,  that  the 
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lated with  the  larger 
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—  9.4°.  Analogous 
proportions,  but  with 
comparatively  higher 
length  averages  and 
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pelle-aux-Saints  values. 

The  general  trend  of 
these  proportional  con- 
ditions may  be  seen 
corroborated  in  Table 
XVI,  in  which  in  the 
males  as  well  as  in  the 
females     the     averages 


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of  the  foramen 
magnum  angle 
decrease  with 
the  increasing 
classification 
of  the  fora- 
men magnum 
length. 

jS.  ANGLE  AND 

INDEX  OF  THE 

FORAMEN 

MAGNUM 

The  aver- 
ages of  the  for- 
amen magnum 
index,  as  spec- 
ified in  Table 
XVII,  decreas- 
ing in  the  San 
Miguel  Island 
series  from  84.8 
to  83.2  in  the 
sexes,  yield  in- 
creasing aver- 
ages of  the  for- 
amen magnum 
angle  of  -  9.4° 
and    -13.2° 


SAN    MIGUEL    ISLAND 


41 


respectively;      while 
the  infantiles,  num- 
bering    only    two, 
with  an  index  aver- 
age  below   those    of 
the  sexes,  come  only 
to    —  9.0°,    a  condi- 
tion   doubtless    due 
to  their  undeveloped 
physical  state.     The 
different  order  of  in- 
dices in  the  Eskimo, 
i.e.  78.7  in  the  males, 
increasing  to  80.4  in 
the  females,  as  pre- 
viously  pointed   out 
(page    32),    shows 
nevertheless  increas- 
ing averages  of  the 
angle,     —    7.1°    and 
—    9.8°,      indicating 
that  the  order  of  sex 
averages  of  the  fora- 
men magnum  angle, 
i.e.    increasing   from 
male    to    female,    is 
rather  a  stable  one 
and,   at  least  so  far 
as    the    two    human 
varieties     of     Table 


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XVII  are  concerned,  is  independent  of  the  behavior 
of  the  foramen  magnum  index  averages  of  the  sexes. 
While  this  is  probably  the  general  behavior  in 
any  series  of  human  skulls,  the  distinctly  increasing 
order  of  the  angle  averages  in  both  sexes  for  the 
increasing  classes  of  the  foramen  magnum  index,  as 
shown  in  Table  XVIII,  is  quite  interesting. 

y.    FORAMEN   MAGNUM   ANGLE   AND   CRANIAL 
LENGTH 

It  is  shown  in  Table  XIX  that  the  averages  for 
the  cranial  length,  decreasing  naturally  in  the  sexes 
and  immatures,  are  correlated  with  increasing  aver- 
ages of  the  foramen  magnum  angle  so  far  as  the 
sexes  are  concerned.10  The  angle  of  the  immatures, 
on  the  other  hand,  decreases  again  and  with  9.0° 
falls  even  slightly  below  the  average  of  the  males. 
As  previously  mentioned,  this  latter  condition  must 
be  attributed  to  the  undeveloped  state  of  the 
infantile  cranium. 

The  Eskimo  of  the  same  table  present  analogous 
successive  differences  in  the  average  expressions. 
The  slightly  higher  averages  of  the  cranial  length 
are  correlated  with  somewhat  lower  averages  of  the 
foramen  magnum  angle.  This  proportion  is  carried 
to  excess  in  the  La  Chapelle-aux-Saints  skull,  whose 
inordinate  length  of  208  mm.  combines  itself  with  a 

10  See  footnote  9. 


SAN    MIGUEL    ISLAND 


43 


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num angle  and  the 
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gous to  the  foramen 
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angle  as  specified  in 
Table  XVI.  This  is 
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XX  and  is  evident  in 
both  the  males  and  the 
females. 

8.     FORAMEN   MAGNUM 

ANGLE    AND     CRANIAL 

LENGTH-BREADTH 

INDEX 

The  tendency  toward 
relative  shortheaded- 
ness  of  the  females  as 
against  the  males  of  a 


SAN    MIGUEL    ISLAND 


45 


given  group  is  also 
borne  out  in  the 
San  Miguel  Island 
crania  and  the  Es- 
kimo of  Table 
XXI.  The  increas- 
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out  before,  that  the 
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with  regard  to  the 
angle,  a  less  ad- 
vanced condition. 
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breadth  propor- 
tion, on  the  other 
hand,  is  fairly  uni- 
form in  both  vari- 
eties, with  the  ex- 
ception perhaps 
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males  appear  to  be 
slightly  less  meso- 
cranial. 

The  comparatively 
low  index  of  75.0  of 
the  La  Chapelle-aux- 
Saints  cranium  has 
also  the  least  special- 
ized angle  of  -f-  7°, 
the  morphologic  sig- 
nificance of  which, 
however,  lies  with  the 
difference  in  species. 

The  metrical  corre- 
lations in  the  sexes  are 
repeated  by  the  clas- 
sified index-angle  cor- 
relations in  each  of 
them.  It  is  shown  in 
Table  XXII  that  with 
the  increasing  length- 
breadth  index  classes, 
the  sizes  of  the  fora- 
men magnum  angles 
also  steadily  increase. 
The  more  advanced 
conditions  in  this  re- 
spect are  shown  in  the 
female  cranium,  not 
only     by     higher 


SAN    MIGUEL    ISLAND        47 

angle  averages  for  the  same  classes  of  the  cranial 
length-breadth  index,  but  also  by  the  fact  that  in 
the  lowest  index  class  there  is  no  female  repre- 
sentative, this  being,  however,  fundamentally  a 
question  of  cranial  length-breadth  proportion  in  the 
females  of  our  series.11 


6.     CONCLUSION   AND   SUMMARY 

The  preceding  study  concerns  itself  with  the 
morphologic,  metric,  and  correlative  conditions  of 
the  foramen  magnum  in  the  San  Miguel  Island  series 
of  crania  in  the  collection  of  the  Museum  of  the 
American  Indian,  Heye  Foundation.  Regarding 
its  shape,  the  foramen  magnum  with  most  cranial 
series  shares  a  certain  indefiniteness  which  in  the 
present  series  is  signified  by  a  slight  predominance 
of  the  circular.  The  frequency  of  this  shape,  how- 
ever, is  approached  by  that  of  the  elliptic,  and,  to  a 
lesser  degree,  by  the  anteriorly  pointed  oval.  The 
latter  two  when  combined  exceed  the  frequency  of 
the  former.  Anomalous  formations  around  the 
foramen  magnum  such  as  the  "manifestations  of 
the  occipital  vertebra"  {Kollmann)  do  not  occur. 
In  a  number  of  cases  notch-like  dilatations  were  ob- 
served, too  unpronounced,  however,  to  assume  a 
missing  ossiculum  Kerckringii,  but  due  nevertheless 
to  irregular  ossification  (fig.  3,  b-c). 

11  In  respect  to  this  see  footnote  9. 


48  SKULLS    FROM 

The  absolute  length  and  width  dimensions  of  the 
foramen  magnum  show  in  their  average  conditions 
the  typical  differences,  more  or  less  stressed,  be- 
tween the  sexes  and  between  these,  i.e.  the  matures 
and  the  immatures,  in  a  diminishing  order  according 
to  the  differences  in  physical  size.  The  average  ex- 
pressions for  the  length  and  width  are  both  markedly 
low  and  rise  in  comparison  only  slightly  above  the 
lowest  values  of  a  racial  range  of  variation.  The 
limited  dimensions  of  the  foramen  magnum  are 
likewise  evidenced  by  its  module  which  in  consider- 
ation of  the  nature  of  the  measurements  ranges  on 
the  average  distinctly  below  the  tribal  varieties  of 
Table  V. 

The  length-width  index  as  a  proportional  expres- 
sion of  the  two  principal  dimensions  of  the  foramen 
magnum  corroborates  the  results  of  the  visual 
examination.  Its  average  signifies  a  somewhat 
rounded  foramen  with  a  slight  tendency  to  narrow 
from  side  to  side,  which  is  more  noticeable  in  the 
females,  and  in  the  latter  appears  to  be  the  rather 
general  occurrence  in  the  human  varieties.  Excep- 
tions to  this  statement  occur,  while  on  the  other  hand 
the  generally  close  approximation  of  the  sex  averages 
may  show  stronger  divergences,  as,  for  instance,  in 
the  Japanese  and  Paltacalo  Indians  with  male  and 
female  averages  of  83.4  and  72.6,  and  88.0  and  79.5 
respectively. 

Investigation  of  the  angular  position  of  the  fora- 
men magnum  plane  in  the  cranial  complex  in  relation 


SAN    MIGUEL    ISLAND        49 

to  the  general  plane  of  orientation,  i.e.  the  ear-eye 
plane,  reveals  several  interesting  results.  The  aver- 
age angularity  is  marked  by  unmistakable  differences 
in  the  human  varieties.  The  San  Miguel  averages, 
for  instance,  when  compared  with  Fr.  Sarasin's 
European  average  of  —  12°,  almost  equal  it,  while 
the  Eskimo  fall  distinctly  lower,  as  do  in  turn  the 
New  Caledonians  and  the  human  fossil.  If  this 
signifies  racial  characteristics,  these  are  still  further 
emphasized  by  the  marked  sex  differences  in  each 
case  which  yield  the  higher  averages  to  the  females. 
The  cause  for  this  remarkable  distinction,  as  sug- 
gested in  footnote  9,  must  be  attributed  quite 
probably  to  sex  differences  of  physical  growth  and 
type  which  primarily  govern  all  and  every  physical 
formation  and  which,  in  this  specific  case  of  the 
brain,  influence  commensurably  the  form  of  the  skull; 
this  may,  in  consequence,  result  in  the  increased 
declination  of  the  foramen  magnum  plane.  Quanti- 
tatively expressible,  this  distinction  stands  out  quite 
clearly,  while  physiologically  no  satisfactory  expla- 
nation can  yet  be  offered. 

The  systematic  investigation  of  the  mutual  or 
correlative  relations  between  certain  cranial  and 
foramen  magnum  measurements  and  proportions 
results  in  a  number  of  interesting  observations.  The 
investigation  was  carried  on  in  such  a  way  that  the 
sex  averages  of  a  special  measurement,  as  well  as 
the  averages  derived  from  its  suitably  divided  range 
of   variation,    were   placed   in   contrast   to   the   sex 


50  SKULLSFROM 

averages  of  another  measurement  to  which  they 
were  to  be  compared,  and  to  those  averages  of  the 
latter  as  checked  with  the  divisions  or  classes  of  the 
first  measurement.  This  is  shown  in  the  subjoined 
table  of  correlations. 

Definite  correlations,  holding  good  for  both  the 
sex  and  class  averages,  could  be  established  between 
the  principal  dimensions  of  both  the  cranium  and 
the  foramen  magnum  to  the  extent  that  the  increas- 
ing cranial  length  and  breadth  were  correlated  with 
increasing  length  and  width  of  the  foramen  magnum 
and  naturally  for  the  modules  implicating  the  addi- 
tional cranial  height  measurement  in  the  cranial 
module.  The  same  gradual  increase  was  observed 
in  the  divisional  correlations  as  based  on  the  classes 
of  the  cranial  length-breadth  index,  but  not  with 
regard  to  the  sex  averages  which,  increasing  in  the 
order  male-female,  encountered  decreasing  foramen 
magnum  sex  averages  in  the  San  Miguel  Island 
skulls,  while,  for  instance,  in  the  Western  Eskimo 
and  Australians,  the  first,  i.e.  increasing  order,  was 
retained.  This  condition  is  reencountered  in  the 
combination  with  the  foramen  magnum  angle  where 
the  foramen  magnum  index  is  used  as  a  base.  The 
conflicting  order  of  graduation  of  sex  averages  in 
the  latter,  i.e.  either  increasing  or  decreasing  in  the 
human  varieties,  as  pointed  out  in  the  preceding 
sentence,  is  correlated,  however,  under  both  these 
conditions  with  only  increasing  averages  of  the  angle. 
The  increasing  class  averages  of  the  foramen  magnum 


Table  of  Mutual  Relations  {Correlations)  between  Average  Foramen  Magnum  and  Cranial 
Metrical  Quantities  in  the  Sexes  and  the  Graded  Divisions  of  Ranges  of  Variation  of  Basic 
Measurements,  in  Descriptive  Terms.  The  Metrical  Accounts  may  be  Looked  for  in  the 
Various  Tables. 


Classification 

Correlated  metrical  quantities 

Cranial  length 

Foramen  magnum  length 

Sexes 

Increasing 

Increasing 

Classes 

Increasing 

Increasing 

Cranial  breadth 

Foramen  magnum  width 

Sexes 

Increasing 

Increasing 

Classes 

Increasing  (only  slightly) 

Increasing 

Cranial  L-Br  index 

Foramen  magnum  index 

Sexes 

Increasing 

f  Decreasing  (San  Miguel  Is.) 

Classes 

Increasing 

\  Increasing  (Western  Eskimo, 
[      Australians) 
Increasing 

Cranial  module 

Foramen  magnum  module 

Sexes 

Increasing 

Increasing 

Classes 

Increasing 

Increasing 

Foramen  magnum  length 

Foramen  magnum  angle 

Sexes 

Decreasing 

Increasing 

Classes 

Increasing 

Decreasing 

Foramen  magnum  index 

Foramen  magnum  angle 

Sexes 

Decreasing  1         .,.   ,  ..          , 
Increasing ?  j  see  third  item  above 

Increasing 

Classes 

Increasing 

Increasing 

Cranial  length 

Foramen  magnum  angle 

Sexes 

Decreasing 

Increasing 

Classes 

Increasing 

Decreasing 

Cranial  L-Br  index 

Foramen  magnum  angle 

Sexes 

Increasing 

Increasing 

Classes 

Increasing 

Increasing 

SAN    MIGUEL    ISLAND        51 

index,  on  the  other  hand,  are  prompted  by  increasing 
averages  of  the  angle.  Identical  results  were  ob- 
served in  the  combinations  of  the  cranial  and 
foramen  magnum  lengths  with  the  foramen  magnum 
angle  in  such  a  way  that  with  the  decreasing  length 
averages  in  the  sexes  in  the  order  male-female,  the 
averages  of  the  angle  increased  while  the  increasing 
class  averages  were  correlated  with  decreasing 
averages  of  the  angle.  There  is  another  phenomenon 
implicated  in  this,  namely,  the  higher  foramen 
magnum  angle  in  the  female  skull,  i.e.  its  greater 
minus  angle  (page  23,  Table  VI)  as  correlated  with 
the  smaller  absolute  cranial  and  foramen  magnum 
lengths,  and  vice  versa.  The  proportions,  however, 
between  the  cranial  length-breadth  index  and  the 
foramen  magnum  angle  show  an  even  progression 
in  the  sexes  as  well  as  in  the  classes. 

i  The  infantile  values,  although  recorded  in  the 
tables,  naturally  have  no  significance  from  the 
viewpoint  of  systematic  comparison.  Of  greater 
import  are  the  findings  upon  the  human  fossil 
(La  Chapelle-aux-Saints)  which  with  its  larger 
dimensions  combines  morphologically  inferior  traits 
of  the  foramen  magnum,  particularly  with  regard  to 
the  excessive  length  of  the  latter  and  to  its  markedly 
low  foramen  magnum  angle  (+  7°)  of  phylogenetic 
significance. 

The  investigations  carried  on  in  the  study  of  the 
foramen  magnum  of  the  San  Miguel  Island  skulls 
give  rise  to  the  following  summarization: 


52  SKULLS    FROM 

1.  The  shape  of  the  foramen  magnum  is  roundish. 

2.  Its  size  is  submedium  to  small,  with  the  typical 
sex  difference  according  to  physical  size. 

3.  The  somewhat  smaller  average  of  the  length- 
width  index  indicates  in  the  females  a  slightly 
narrower  foramen  magnum  as  compared  with  that 
of  the  males.  This  condition  is  shown  to  vary  in 
the  human  varieties. 

4.  The  greater  degree  of  minus  declination  of  the 

foramen  magnum  plane  in  the  female  crania,   also 

in  other  human  groups,   signifies  a  more  advanced 

morphologic  condition. 

Size  and  type  differences  in  the  brain,  regarding  which 
no  studies  have  as  yet  been  made,  are  doubtless  causative 
for  the  varying  conditions  of  cranial  morphology  in  the 
sexes. 

5.  The  study  of  mutual  relations  between  different 
measurements  reveals  the  following  correlations: 

a.  Simultaneous  increase  in  absolute  cranial  and 

foramen  magnum  measurements. 

b.  Varying  behavior  between  the  sex  averages  of 

the  cranial  L-Br  index  and  the  foramen 
magnum  index,  i.e.  increasing-decreasing  in 
the  San  Miguel  Island  skulls,  but  simultan- 
eously increasing  in  a  number  of  other  human 
varieties.  A  simultaneous  increase,  however, 
is  the  distinguishing  mark  of  the  class  cor- 
relation between  the  indices  in  question. 

c.  Foramen  magnum  and  cranial  lengths  are  cor- 

related with  the  foramen  magnum  angle  in 
such  a  way  that  with  the  decrease  in  the  sex 


SAN    MIGUEL    ISLAND        53 

averages  of  the  former,  increasing  averages  of 
the  angle  are  observed,  while  in  corroboration 
the  increasing  averages  of  the  subdivided 
ranges  of  the  former  are  prompted  by  the 
decreasing  averages  of  angularity. 

d.  The  foramen  magnum  index,  varying  in  regard 

to  the  graduation  of  sex  averages  in  various 
human  groups,  is  correlated  with  invariably 
increasing  sex  averages  of  the  angle;  but 
simultaneous  increase  of  averages  obtains  in 
the  classified  averages  of  both  categories. 

e.  Simultaneous  increase  of  sex  as  well  as  class 

averages  was  observed  between  the  cranial 
L-Br  index  and  the  foramen  magnum  angle.12 


LITERATURE 
Bolk,  Louis 

1915     Uber   Lagerung,    Verschiebung    und    Neigung 
des    Foramen     magnum    am    Schadel     der 
Primaten.     Ztschr.   Morph.  Anthr.,  v.  xvn, 
pp.  688-692. 
Cameron,  John 

1923     Osteology  of  the  Western  and  Central  Eskimos. 
Rep.    Canadian   Arct.    Exped.,    1913-18,    v. 
xii,  pt.  c. 
Hannover,  Adolphus 

1881  Le  cartilage  primordial  et  son  ossification  dans 
le  crane  humain  avant  la  naissance.  (Orig- 
inal Danish,  1879-80.) 

12  Experiment  with  a  number  of  other  more  or  less 
closely  related  measurements  of  the  cranium  to  those  of 
the  foramen  magnum  not  recorded  here,  revealed  similarly 
identical  correlations. 

Higher  mathematical  differential  methods  (coefficient 
of  correlation)  were  not  resorted  to  on  account  of  the 
relatively  small  series  of  specimens  under  investigation. 


54        SAN    MIGUEL    ISLAND 

Hooton,  Earnest  A. 

1920     Indian  village  site  and  cemetery  near  Madi- 

sonville,  Ohio.     Pap.  Peabody  Mus.  Amer. 

Archaeol.    Ethnol.    Harvard    Univ.,    v.    viii, 

no.  1,  pp.  83-137. 
Hrdlicka,  Ales 

1906  Contribution  to  the  physical  anthropology  of 

California.      Univ.  Cat.  Publ.  Amer.  Archaeol. 
Ethnol.,  v.  iv,  no.  2,  pp.  49-64. 

1907  Skeletal  remains  suggesting  or  attributed  to 

early  man  in  North  America.     Bull.  33  Bur. 

Amer.  Ethnol.,  Washington. 
1909     Report  on  an  additional  collection  of  skeletal 

remains     from     Arkansas     and    Louisiana, 

Jour.  Acad.  Nat.  Sci.  Philadelphia,  v.  xiv, 

pp.  173-249. 
1916     Physical  anthropology  of  the  Lenape  or  Dela- 

wares,  and  of  the  eastern  Indians  in  general. 

Bull.    62    Bur.    Am.    Ethnol.,    Washington. 

(Reprinted  as  Contributions  Mus.  Amer.  Ind. 

Heye  Found.,  v.  in.) 
Klaatsch,  Hermann 

1908  The  skull  of  the  Australian  aboriginal.     Rep. 

Path.  Lab.  Lunacy  Dept.  Sydney,  v.  I,  pt.  3, 
pp.  43-167. 
Martin,  Rudolf 

1928     Lehrbuch    der   Anthropologic     2d.  ed.     Jena. 
Oetteking,  Bruno 

1920  Morphological  and  metrical  variation  in  skulls 
from  San  Miguel  Island,  California.  I. — 
The  sutura  nasofrontalis.  Indian  Notes 
and  Monogr.,  v.  vn,  no.  2,  pp.  51-85. 

1923  On  the   morphological  significance  of  certain 

cranio-vertebral  variations.     Anat.  Rec,  v. 
xxv,  pp.  339-353. 

1924  Declination  of  the  pars  basilaris  in  normal  and 

artifically    deformed  skulls.     Indian    Notes 
and  Monogr.,  Misc.  no.  27. 
Sarasin,  Fritz 

1916-22     Anthropologie     der  Neu-Caledonier     und 

Loyalty-Insulaner.  C.     Anthropologie. 

Berlin.  7  q  £~  Q  \    n  1 

f   u  J  C3  1    / 


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